Graceful small-headed sea snake - Hydrophis gracilis [now Microcephalophis gracilis]
The graceful small-headed sea snake, or slender sea snake, is one of the members of the Hydrophiidae, a family of highly-venomous seafaring reptiles. Though they can function on land, many members of this species spend effectively their entire life at sea. Their habitat - the Indian Ocean, South China Sea, and Persian Gulf - has an average water temperature high enough to allow these snakes to not need any time “sunning” themselves.
Despite their highly venomous nature, most sea snakes (including this species) are very placid. They rarely bite, even when threatened - not that I’d advocate you approaching one! - but as they must hunt fish that are faster than them in the water, their venom is potent enough to immediately immobilize and kill even their largest prey.
Transactions of the scientific meetings of the Zoological Society of London. 1841.